This invention relates generally to microwave devices and in particular to a method and apparatus for assembling a low cost ferrite stripline circulator.
As is known in the art, energy transfer between two or more ports may be provided by non-reciprocal devices such as circulators and isolators. In particular with circulators, energy fed to an input port of the circulator is transferred to an output port of the circulator, whereas input energy fed to the output port of the circulator is not efficiently transferred to the input port of the circulator, and therefore, such a device is generally referred to as a non-reciprocal device. Such devices are used to minimize VSWR interactions between adjacent components or to duplex a common antenna between a transmitter and a receiver.
One type of circulator commonly employed in the art is a junction circulator which can be comprised of either a stripline transmission medium or microstrip transmission medium. The construction of a stripline circulator is shown in Microwave Circulator Design, Douglas K. Linkhart, Artech House, Inc., MA 1989, pages 37-39. A junction circulator typically comprises three ports and is generally referred to in the art as a Y-junction circulator. The basic construction of a stripline Y-junction circulator includes a center conductor having three stripline branches connected to a center portion. The center conductor is sandwiched between a pair of ferrite disks which space said center conductor from ground planes disposed over the second surfaces of the ferrite disks. Disposed over the second surfaces of the ground planes are permanent magnets which magnetically bias the ferrite. The ferrites are used to provide nonreciprocal performance via gyromagnetic action. Input energy fed to an input one of the branches of the circulator is transferred either to a clockwise disposed or counter-clockwise disposed adjacent output port of the circulator in accordance with the polarity of the magnetic field fed through the ferrite disks. Screw clamps, soldering or epoxy techniques usually hold the circulators together and in place.
Many microwave systems require ferrite circulators with stripline, microstrip or coaxial transmission line interfaces. Solid state phased array systems require large quantities of circulators (typically one to three per transmit/receive (T/R) module. In order to reduce system costs components that are used repetitively such as circulators are key targets for cost reduction. Prior art circulators have been implemented with solder joints, epoxy bonds or conventional fasteners which contribute to the circulator cost and they are not easily disassembled for rework without damage to the parts in a unit. Accordingly, there is a need for a simply assembled, low cost microwave ferrite circulator.